I ordered a Spuhr mount today from Mile High (great helpful bunch they are there, too!) before I read all of the benefits they tout for the mount. Afterwards I looked at all the accessories I could add down the road and notice that they sell the 10 degree leveling key separately. Does this mean they don't include one with the scope? Aye aye aye, talk about a la carte!
If I do have to buy it separately, I'd sure opt for the "kit" with the little picatinny adapter... that would sure be a handy piece, and could be used to level a scope on any mount or rail where the 2 pieces would fit.
Incidentally, while I was puttering around in my shop today mounting a scope on a one piece mount, I was thinking about the popular stack-shims-between-the-scope-and-mount method. Note that I have precision gauge blocks and gauge pins so I can always use the shim method but I happened to glance at a precision square lying on a bench and had a brainstorm.
One of the "blades" of the right-angle square (a toolmakers square is a fixed, hardened and ground piece) is a little wider than the gap between the scope and mount. By inserting the blade between the scope and mount (at right angles to the scope axis) and twisting, I create an infinitely adjustable "shim" between the 2 pieces. It takes about 1/10th the time to do it that way vs. playing with various combinations of shim thickness (or in my case stacked gauge blocks) with the same result... the bottom flat of the scope is parallel to the top of the scope base.
All you need to do this is something flat with 2 parallel edges whose width is greater than the gap between the scope and mount/rail. A 6" metal scale or some flat bar stock would work as well.